1. Technical Field
The present invention relates to a levelling system for a camera crane.
When a film or video camera is mounted on a remote head secured to a levelling head fixed to the end of a boom of a crane so that the camera can move during filming, it is essential that a platform on which the camera is supported be maintained level at all times.
2. Prior Art
Camera cranes have been employed in the past. However, since it has been necessary to employ a fixed mechanical (parallelogram) arrangement for keeping the camera remote head level during crane movement, it has only been possible to carry out luffing motion to change the elevation of the crane or slewing motion to rotate the crane boom about a vertical supporting pivot during filming. The boom length can only be altered by removing and refitting the mechanical linkage of the levelling system. It will be appreciated that more spectacular effects can be created if not only the elevation but the boom length of the camera crane can be moved during filming while maintaining the camera remote head level at all times.
On some existing camera cranes, a platform or levelling plate is provided at the end of the boom. This platform is sufficiently large to allow a camera operator and his assistant to sit on it together with the camera mounted on a tripod which also rests on the platform. Since filming during crane movement from such a platform can be dangerous, it is preferred to mount the camera on a remote head which allows the camera to be rotated about a vertical and a horizontal axis relative to the levelling plate to which the remote head is fitted. A typical electrically controllable remote head of this type is manufactured by Technovision Cameras Ltd. This remote head is provided with electrical connections via slip-rings so that there is no limitation of rotation of the camera in either axis. Movement of the camera as well as all camera functions, such as the power control, the running control, focus, iris and zoom controls are remotely controllable from the ground by electrical means. In implementing the present invention, it is proposed to use such a conventional remote head.